几道高一英语词形变化题,

题目

几道高一英语词形变化题,
1.The experience we gained in this area ( ) very helpful for our research.
括号内词语用 prove 变形,还有原因
2.Mother doesn't let him go out alone unless he ( ) to come back before dark.
括号内填promise变形,是写promised么?

答案

1. proved
prove更多时候做系动词,意思是“证明是”,不用于被动语态.
因为前句有gained,所以也使用其过去式proved.
2. promises
主从句时态一致,所以也用一般现在时.
主语he为第三人称单数,所以用单数形式promises.